A push-pull control output circuit with positive and negative input protection

Abstract

The present invention discloses a push-pull control output circuit with positive and negative input protection, including a push-pull output module, a positive / negative voltage input protection module and an overcurrent detection protection module electrically connected to each other: the push-pull output module is connected to a power supply, and is used to convert a control input signal OutD_Ctr at a VCC power supply end into a drive output signal OUTD at a VCC_D power supply end; the positive / negative voltage input protection module is used to cut off the power supply circuit to prevent current backflow when the push-pull output module is mistakenly connected to a positive / negative voltage input power supply; the overcurrent detection protection module is used to monitor the output terminal current of the push-pull output module to perform overcurrent protection on it. The present invention can achieve tolerance of positive / negative voltage input of an external power supply, effectively avoid damage to the output circuit caused by mistaken connection to a power supply, and has high reliability.

Description

Technical Field

[0001] The present invention relates to the technical field of electronic circuits, and in particular to a push-pull control output circuit with positive and negative input protection. Background Art

[0002] Control output circuits are widely used in the field of control signals, especially the output ports of programmable logic controllers (PLCs). Currently used control output circuits generally do not have overcurrent protection functions and lack effective protection measures against short circuits. When the external input power supply or even negative voltage is applied, the circuit will be damaged in a short time, causing the signal to be out of control and causing irreversible failures in the system. Summary of the invention

[0003] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a push-pull control output circuit with positive and negative input protection, so as to solve the problem that the control output circuit in the prior art lacks effective protection measures and may be damaged in a short time when the external input power supply is even negative voltage.

[0004] In order to solve the above technical problems, the present invention is implemented by adopting the following technical solutions:

[0005] The present invention provides a push-pull control output circuit with positive and negative input protection, comprising a push-pull output module, a positive / negative voltage input protection module and an overcurrent detection protection module electrically connected to each other:

[0006] The push-pull output module is connected to the power supply and is used to convert the control input signal OutD_Ctr of the VCC power supply end into the driving output signal OUTD of the VCC_D power supply end;

[0007] The positive / negative voltage input protection module is used to cut off the power supply circuit to prevent current backflow when the push-pull output module is mistakenly connected to the positive / negative voltage input power supply;

[0008] The overcurrent detection protection module is used to monitor the output current of the push-pull output module to perform overcurrent protection on it.

[0009] Optionally, the push-pull output module includes a first NPN transistor, a second NPN transistor, a third PNP transistor, a fourth PNP transistor, a fourth resistor, a sixth resistor and a seventh resistor;

[0010] The emitter of the first NPN transistor, the emitter of the fourth PNP transistor, one end of the fourth resistor and one end of the seventh resistor are all connected to one end of the sixth resistor; the bases of the first NPN transistor and the fourth PNP transistor are all connected to the other end of the sixth resistor; the other end of the fourth resistor is connected to the VCC power supply terminal, the other end of the sixth resistor is connected to the signal input terminal, and the other end of the seventh resistor is grounded;

[0011] The collectors of the first NPN transistor and the fourth PNP transistor are respectively connected to the bases of the third PNP transistor and the second NPN transistor, the collectors of the third PNP transistor and the second NPN transistor are both connected to the signal output terminal, the emitter of the third PNP transistor is connected to the VCC_D power supply terminal, and the emitter of the second NPN transistor is grounded.

[0012] Optionally, the push-pull output module further includes a fifth resistor, and the signal input end is connected to the other end of the sixth resistor through the fifth resistor.

[0013] Optionally, the overcurrent detection protection module includes a first PNP transistor, a third NPN transistor, a first resistor and an eighth resistor;

[0014] The collector and base of the first PNP transistor are respectively connected to the base and emitter of the third PNP transistor, and the emitter of the first PNP transistor is connected to the VCC_D power supply terminal; the two ends of the first resistor are respectively connected to the emitter and base of the first PNP transistor;

[0015] The collector and base of the third NPN transistor are respectively connected to the base and emitter of the second NPN transistor, and the emitter of the third NPN transistor is grounded; the two ends of the eighth resistor are respectively connected to the emitter and base of the third NPN transistor.

[0016] Optionally, the first resistor and the first PNP transistor form a constant current source circuit to limit the output current of the third PNP transistor; the eighth resistor and the third NPN transistor form a constant current source circuit to limit the input current of the second NPN transistor.

[0017] Optionally, the overcurrent detection protection module further includes a ninth sampling resistor and a tenth sampling resistor, one end of each of the ninth sampling resistor and the tenth sampling resistor is connected to the control unit MCU, the other end of the ninth sampling resistor is connected to the signal output end, and the other end of the tenth sampling resistor is grounded;

[0018] The control unit MCU is used to determine whether the output current is too large according to the data fed back by the ninth sampling resistor and the tenth sampling resistor, so as to perform overcurrent protection on the second NPN transistor.

[0019] Optionally, the positive / negative voltage input protection module includes a second PNP transistor, a second resistor, a third resistor, a first voltage stabilizing diode, a second diode and a third diode;

[0020] The collector and emitter of the second PNP transistor are connected to the base and emitter of the third PNP transistor respectively;

[0021] Two ends of the second resistor are respectively connected to the base of the second PNP transistor and the emitter of the third PNP transistor;

[0022] Two ends of the third resistor are respectively connected to the base of the second PNP transistor and the negative terminal of the first voltage zener diode, and the positive terminal of the first voltage zener diode is connected to the collector of the third PNP transistor;

[0023] The cathode terminal of the second diode and the anode terminal of the third diode are both connected to the signal output terminal, the anode terminal of the second diode is connected to the collector of the third PNP transistor, and the cathode terminal of the third diode is connected to the collector of the second NPN transistor.

[0024] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0025] The present invention connects a positive / negative voltage input protection module and an overcurrent detection protection module in the circuit of a push-pull output module, thereby not only being able to provide overcurrent protection for the output circuit, but also being able to tolerate the positive / negative voltage input of an external power supply, thereby effectively avoiding damage to the output circuit caused by incorrect access to the power supply, and providing reliable protection for the safe and stable operation of power devices, having strong versatility and a very wide range of applications;

[0026] Among them, the second diode and the third diode in the positive / negative voltage input protection module are connected to the signal output end, which can prevent damage caused by an external voltage higher than the circuit power supply voltage entering the circuit; the first voltage regulator is turned on when the negative voltage power supply is connected to quickly shut down the voltage output. This circuit can effectively prevent damage caused by the connection of external voltage sources for positive and negative inputs; the control unit MCU monitors the output terminal voltage by detecting the voltage of the ninth sampling resistor and the tenth sampling resistor to detect overcurrent conditions, thereby effectively protecting the drive circuit. It has high reliability, is easy to implement, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0028] Figure 1 is a circuit diagram of a push-pull output module provided by an embodiment of the present invention;

[0029] Figure 2 Schematic diagram of a push-pull control output circuit with positive and negative input protection provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0030] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and cannot be used to limit the protection scope of the present invention.

[0031] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and the like are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first", "second", and the like may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0032] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood by specific circumstances.

[0033] Reference Figure 1 and Figure 2 The push-pull control output circuit with positive and negative input protection provided by an embodiment of the present invention includes a push-pull output module, a positive / negative voltage input protection module and an overcurrent detection protection module electrically connected to each other: wherein the push-pull output module is connected to a power supply and is used to convert a control input signal OutD_Ctr at a VCC power supply end into a drive output signal OUTD at a VCC_D power supply end; the positive / negative voltage input protection module is used to cut off a power supply circuit to prevent current backflow when the push-pull output module is mistakenly connected to a positive / negative voltage input power supply; and the overcurrent detection protection module is used to monitor the output current of the push-pull output module to perform overcurrent protection thereon.

[0034] Specifically, the push-pull output module includes a first NPN transistor TN1, a second NPN transistor TN2, a third PNP transistor TP3, a fourth PNP transistor TP4, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6 and a seventh resistor R7; Figure 1 As shown, the emitter of the first NPN transistor TN1, the emitter of the fourth PNP transistor TP4, one end of the fourth resistor R4 and one end of the seventh resistor R7 are all connected to one end of the sixth resistor R6; the base of the first NPN transistor TN1, the base of the fourth PNP transistor TP4 and one end of the fifth resistor R5 are all connected to the other end of the sixth resistor R6; the other end of the fifth resistor R5 is connected to the signal input end, the other end of the fourth resistor R4 is connected to the VCC power supply end, and the other end of the seventh resistor R7 is grounded; in addition, the collectors of the first NPN transistor TN1 and the fourth PNP transistor TP4 are respectively connected to the bases of the third PNP transistor TP3 and the second NPN transistor TN2, the collectors of the third PNP transistor TP3 and the second NPN transistor TN2 are both connected to the output signal end, the emitter of the third PNP transistor TP3 is connected to the VCC_D power supply end, and the emitter of the second NPN transistor TN2 is grounded. This embodiment converts the low voltage control input signal OutD_Ctr whose high level voltage is VCC into the driving output signal OUTD whose high level voltage is VCC_D and has a certain current driving capability through the design of the push-pull output circuit.

[0035] As an embodiment of the present invention, the overcurrent detection protection module includes a first PNP transistor TP1, a third NPN transistor TN3, a first resistor R1 and an eighth resistor R8; wherein, the collector and base of the first PNP transistor TP1 are respectively connected to the base and emitter of the third PNP transistor TP3, and the emitter of the first PNP transistor TP1 is connected to the VCC_D power supply terminal; the two ends of the first resistor R1 are respectively connected to the emitter and base of the first PNP transistor TP1, and the first resistor R1 and the first PNP transistor TP1 form a constant current source circuit to limit the output current of the third PNP transistor TP3. The collector and base of the third NPN transistor TN3 are respectively connected to the base and emitter of the second NPN transistor TN2, and the emitter of the third NPN transistor TN3 is grounded; the two ends of the eighth resistor R8 are respectively connected to the emitter and base of the third NPN transistor TN3, and the eighth resistor R8 and the third NPN transistor TN3 form a constant current source circuit to limit the input current of the second NPN transistor TN2.

[0036] In addition, the overcurrent detection protection module also includes a ninth sampling resistor R9 and a tenth sampling resistor R10, one end of the ninth sampling resistor R9 and the tenth sampling resistor R10 are connected to the control unit MCU, the other end of the ninth sampling resistor R9 is connected to the signal output end, and the other end of the tenth sampling resistor R10 is grounded; the control unit MCU of the control output circuit monitors the output end voltage by detecting the data fed back by the ninth sampling resistor R9 and the tenth sampling resistor R10, thereby detecting the overcurrent situation to perform overcurrent protection on the second NPN transistor TN2.

[0037] As an embodiment of the present invention, the positive / negative voltage input protection module includes a second PNP transistor TP2, a second resistor R2, a third resistor R3, a first voltage zener diode D1, a second diode D2 and a third diode D3; specifically, the collector and emitter of the second PNP transistor TP2 are respectively connected to the base and emitter of the third PNP transistor TP3; the two ends of the second resistor R2 are respectively connected to the base of the second PNP transistor TP2 and the emitter of the third PNP transistor TP3; the two ends of the third resistor R3 are respectively connected to the base of the second PNP transistor TP2 and the negative end of the first voltage zener diode D1, and the positive end of the first voltage zener diode D1 is connected to the collector of the third PNP transistor TP3; the negative end of the second diode D2 and the positive end of the third diode D3 are both connected to the signal output end, the positive end of the second diode D2 is connected to the collector of the third PNP transistor TP3, and the negative end of the third diode D3 is connected to the collector of the second NPN transistor TN2. Among them, the first voltage stabilizing diode D1 is turned on when it detects that the output is connected to a negative voltage, and the third PNP transistor TP3 is quickly turned off through the second PNP transistor TP2; the second diode D2 is reversely cut off when the output is connected to a positive voltage to prevent high voltage from flowing back to the VCC_D power supply terminal.

[0038] The working principle of the push-pull control output circuit with positive and negative input protection provided by the embodiment of the present invention is as follows: Figure 2As shown, when the control output is high and a negative voltage is connected externally, the first voltage zener diode D1 is subjected to the voltage of the control output and the external voltage and breaks down, and the breakdown causes the second PNP transistor TP2 and the first PNP transistor TP1 to be turned on, thereby turning off the third PNP transistor TP3 in the main power tube; when the control output is high and a higher level input is externally provided, the second diode D2 will be turned off to prevent current from being injected; when the control output is low and a high level short circuit is externally provided, the control unit MCU calculates the output current by detecting the voltage of the ninth sampling resistor R9 and the tenth sampling resistor R10 of the voltage feedback, thereby actively turning off the second NPN transistor TN2 in the power tube for overcurrent protection; when the control output is low and a negative level input is externally provided, the third diode D3 will be turned off to prevent current from being injected; thereby completely protecting against damage caused by direct input of positive and negative input power supplies, and providing reliable protection for the safe and stable operation of power devices.

[0039] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A push-pull control output circuit with positive and negative input protection, characterized in that: It includes a push-pull output module, a positive / negative voltage input protection module and an overcurrent detection protection module which are electrically connected to each other: The push-pull output module is connected to the power supply and is used to convert the control input signal OutD_Ctr of the VCC power supply end into the driving output signal OUTD of the VCC_D power supply end; The positive / negative voltage input protection module is used to cut off the power supply circuit to prevent current backflow when the push-pull output module is mistakenly connected to the positive / negative voltage input power supply; The overcurrent detection protection module is used to monitor the output current of the push-pull output module to perform overcurrent protection on it; The push-pull output module includes a first NPN transistor, a second NPN transistor, a third PNP transistor, a fourth PNP transistor, a fourth resistor, a sixth resistor and a seventh resistor; The emitter of the first NPN transistor, the emitter of the fourth PNP transistor, one end of the fourth resistor and one end of the seventh resistor are all connected to one end of the sixth resistor; the bases of the first NPN transistor and the fourth PNP transistor are all connected to the other end of the sixth resistor; the other end of the fourth resistor is connected to the VCC power supply terminal, the other end of the sixth resistor is connected to the signal input terminal, and the other end of the seventh resistor is grounded; The collectors of the first NPN transistor and the fourth PNP transistor are respectively connected to the bases of the third PNP transistor and the second NPN transistor, the collectors of the third PNP transistor and the second NPN transistor are both connected to the signal output terminal, the emitter of the third PNP transistor is connected to the VCC_D power supply terminal, and the emitter of the second NPN transistor is grounded.

2. The push-pull control output circuit with positive and negative input protection according to claim 1, characterized in that: The push-pull output module further includes a fifth resistor, and the signal input end is connected to the other end of the sixth resistor through the fifth resistor.

3. The push-pull control output circuit with positive and negative input protection according to claim 1, characterized in that: The overcurrent detection protection module includes a first PNP transistor, a third NPN transistor, a first resistor and an eighth resistor; The collector and base of the first PNP transistor are respectively connected to the base and emitter of the third PNP transistor, and the emitter of the first PNP transistor is connected to the VCC_D power supply terminal; the two ends of the first resistor are respectively connected to the emitter and base of the first PNP transistor; The collector and base of the third NPN transistor are respectively connected to the base and emitter of the second NPN transistor, and the emitter of the third NPN transistor is grounded; the two ends of the eighth resistor are respectively connected to the emitter and base of the third NPN transistor.

4. The push-pull control output circuit with positive and negative input protection according to claim 3, characterized in that: The first resistor and the first PNP transistor form a constant current source circuit to limit the output current of the third PNP transistor; the eighth resistor and the third NPN transistor form a constant current source circuit to limit the input current of the second NPN transistor.

5. The push-pull control output circuit with positive and negative input protection according to claim 3, characterized in that: The overcurrent detection protection module further includes a ninth sampling resistor and a tenth sampling resistor, one end of each of the ninth sampling resistor and the tenth sampling resistor is connected to the control unit MCU, the other end of the ninth sampling resistor is connected to the signal output end, and the other end of the tenth sampling resistor is grounded; The control unit MCU is used to determine whether the output current is too large according to the data fed back by the ninth sampling resistor and the tenth sampling resistor, so as to perform overcurrent protection on the second NPN transistor.

6. The push-pull control output circuit with positive and negative input protection according to claim 5, characterized in that: The positive / negative voltage input protection module includes a second PNP transistor, a second resistor, a third resistor, a first voltage stabilizing diode, a second diode and a third diode; The collector and emitter of the second PNP transistor are connected to the base and emitter of the third PNP transistor respectively; Two ends of the second resistor are respectively connected to the base of the second PNP transistor and the emitter of the third PNP transistor; Two ends of the third resistor are respectively connected to the base of the second PNP transistor and the negative terminal of the first voltage zener diode, and the positive terminal of the first voltage zener diode is connected to the collector of the third PNP transistor; The cathode terminal of the second diode and the anode terminal of the third diode are both connected to the signal output terminal, the anode terminal of the second diode is connected to the collector of the third PNP transistor, and the cathode terminal of the third diode is connected to the collector of the second NPN transistor.

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